WikiLeaks announced the start of a new project as it released the first leaked files it said detailed the extent to which surveillance companies were selling information obtained by monitoring people's mobile phones and computers.

Launching the "Spy Files", WikiLeaks founder Julian Assange said: "The reality is, intelligence contractors are selling right now to countries across the world mass surveillance systems for all those products."

He said the release of the documents – 287 today, to be followed by further releases this week and into next year – uncovers a practice which, although lawful, is leading towards a "totalitarian surveillance state".

The project is being jointly undertaken by the group and website and Privacy International among others, and media organisations from six countries, including The Bureau of Investigative Journalism in the UK.

WikiLeaks claimed it was "shining a light on this secret industry that has boomed since September 11, 2001 and is worth billions of dollars per year".

Mr Assange said: "Who has an iPhone? Who has a BlackBerry? Who uses Gmail? Well, you're all screwed." He believed their personaldetails were being traded by intelligence contractors.